The present invention relates to a device for continuously forming a square pipe made of a light-weight, high-strength FRP (fiber reinforced plastic) utilized in an aircraft, or a square pipe made of FRP utilized as an architectural material.
A conventionally known method for forming an FRP square pipe is called a pultrusion (protrusion) method, where fiber is first impregnated with resin before being guided into a heated mold thereby curing the resin. However, this conventional method restricts the ratio of fiber content in the material, and the fiber orientation in the material is easily disordered, so it is difficult to produce a formed product having high quality. On the other hand, a product formed of a prepreg material (fiber impregnated with resin and then semi-cured) can have higher ratio of fiber content and the fiber orientation can be uniform, so such product is used to manufacture high-strength parts used in an aircraft and the like.
A conventional method for forming an FRP square pipe using a prepreg material involves providing a mold-release treatment to a metallic square column to be used as a core, laminating a predetermined number of layers of prepreg sheets to the core, and forming the desired shape by an autoclave. However, when the length of the desired product is long, the autoclave and the device for drawing out the metallic square column after curing the material must also be large, so a larger facility is required.
Another method for forming the FRP square pipe involves using a silicon rubber tube and the like as core, and after laminating the prepreg material to the tube, the laminated material is placed inside an external mold, and inner air pressure is provided to the material to form the desired shape. Only small pulling force is required according to the second method, but an external mold must be prepared, and the method involves another problem related to the durability of the silicon rubber tube.
The present invention provides a device capable of continuously forming a high-quality square pipe using prepreg material, that can be used in an aircraft and the like, and that requires a smaller number of extrinsic equipment.
The device for continuously forming an FRP square pipe according to the present invention comprises a device for sequentially laminating a release film and a prepreg material sheet cut to have predetermined widths onto a square pipe made of aluminum having an outer diameter that is smaller than the inner diameter of the square pipe to be formed, a pre-expansion device placed before a mold for expanding the laminated prepreg material in the radial direction so that its inner diameter matches the inner diameter of the product, and a hot press that is opened and closed corresponding to the movement of a pulling device. The pulling device moves the formed product for a predetermined length when the hot press is opened. The aluminum square pipe functioning as the core is pulled toward the pulling device from the hot press, and is supported by a device capable of taking out the center piece even during the forming process.